1. Field of the Invention
The present invention relates to the field of displaying technology, and in particular to an OLED display device.
2. The Related Arts
An OLED (Organic Light-Emitting Display) device shows excellent displaying performance and also possesses various advantages, such as being self-luminous, simple structure, being ultra-thin, fast response, wide view angle, low power consumption, and being capable of achieving flexible displaying and is thus regarded as a “dream display”, so that it has attracted the attention of major display manufacturers and becomes the mainstream of the third-generation display devices in the field of displaying technology.
The OLED display device is a spontaneous emission display device and is generally made up of a pixel electrode and a common electrode respectively functioning as an anode and a cathode and an organic light emission layer arranged between the pixel electrode and the common electrode. When a proper voltage is applied to the anode and the cathode, the organic light emission layer emits light. The organic light emission layer comprises a hole injection layer formed on the anode, a hole transport layer formed on the hole injection layer, an emissive layer formed on the hole transport layer, an electron transport layer formed on the emissive layer, and an electron injection layer formed on the electron transport layer. Light emitting mechanism is that when driven by a predetermined voltage, electrons and holes are respectively injected into the electron injection layer and the hole injection layer. The electrons and the holes migrate through the electron transport layer and the hole transport layer to the emissive layer and combine with each other in the emissive layer to form excitons that excite light-emitting molecules, the later undergoing radiation relaxation to give off visible light.
Generally speaking, an OLED display device comprises a plurality of pixel zones arranged in a matrix, a pixel separation layer having multiple opening for separating each pixel zones from the remaining pixel zones. Each opening corresponds to one pixel zone. The pixel electrode and the organic light-emitting layer are arranged in the opening and the common electrode is set on the organic light-emitting layer and the pixel separation layer of each pixel zone.
Since the organic light-emitting layer is formed of an organic material and is very sensitive to moisture and oxygen, it may get deteriorated and changed due to invasion of moisture and oxygen. Heretofore, the pixel separation layer is made of an organic material and it has been recognized that when the organic material that makes the pixel separation layer presents an interface contacting the organic light-emitting layer, moisture and oxygen contained in the pixel separation layer may spread through the interface into the organic light-emitting layer, causing a change of the electron state in the organic light-emitting layer and thus resulting in loss of the ideal electric-field induced light emission characteristics and deteriorating the organic light-emitting layer to affect displaying performance. To improve the problem caused by the organic material of the pixel separation layer, a pixel separation layer made of an inorganic material that has less content of moisture and oxygen has been proposed. However, for a pixel separation layer made of an inorganic material, sidewalls that define the opening of the pixel separation layer are generally vertically erected, at approximately 90 degrees, with respect to a substrate, making the portion of the organic light-emitting layer and the common electrode that corresponds to the sidewalls significantly thinner than other portions or even broken, whereby moisture and oxygen may enter the organic light-emitting layer through the thinned or broken portion of the common electrode, leading to deterioration of the light emission characteristics of the organic light-emitting layer. Further, if the organic light-emitting layer is broken at a site of the sidewalls, the distance between the common electrode and the pixel electrode may get extremely close, leading to shorting between the two electrode and thus damaging the organic light-emitting layer.